Converting fujitsu leaf spring keyboard

[CarpCharacin]

I found a Sanyo MBC-885 keyboard for sale with the desktop connector, and I'm thinking about buying it, because I heard that they had Fujitsu leaf spring switches, but I'm just wondering, how difficult would it be to convert it to USB?

[PancakeMSTR]

Long story short - I think it's kind of hard.

I'm also interested in this, though, as I just picked up an Epson something-or-other, I'll post the model number this evening. I believe @snacksthecat has experience with converting Fujitsu leaf springs and could offer some advice/suggestions. He also commented a link to a guide about a year ago, but it doesn't work anymore. I was thinking about asking him if he knew another way to view it.

From a little bit of research I've been doing it looks like the most common way of converting fujitsu leaf spring boards is by handwire, but I was thinking about reaching out to the QMK people/snacksthecat to see if we could figure out how to convert it with its native protocol, although it might be kind of hard.

[snacksthecat]

From a little bit of research I've been doing it looks like the most common way of converting fujitsu leaf spring boards is by handwire, but I was thinking about reaching out to the QMK people/snacksthecat to see if we could figure out how to convert it with its native protocol, although it might be kind of hard.

I took a shot at converting the protocol but the board's limitations made it not worth it (I'll explain below). Haata actually wrote a plug and play converter for it a few years back (well the board is not 5v but once you deal with that) https://github.com/kiibohd/controller/b ... can_loop.c

Controller Replacement
This is the approach I took. You can see some details in the thread I started earlier this year.
https://github.com/kiibohd/controller/b ... can_loop.c
It's actually pretty straight-forward to do. Just a little bit tedious.
However, this approach does not overcome the keyboard's achilles heel; which is that it is only 1KRO.
Which leads me to my revised approach.

Controller Replacement + Diode Mod
I ended up cutting the traces on the PCB and wiring in diodes for each switch. By doing that, I can take advantage of NKRO. This was a painful process but it turned out pretty good.

If you need any help, feel free to reach out.

Edit: My comment is specifically about the Epson QX-10 keyboard

[PancakeMSTR]

Controller Replacement
This is the approach I took. You can see some details in the thread I started earlier this year.
https://github.com/kiibohd/controller/b ... can_loop.c
It's actually pretty straight-forward to do. Just a little bit tedious.
However, this approach does not overcome the keyboard's achilles heel; which is that it is only 1KRO.
Which leads me to my revised approach.

Fantastic, I'll take a look!

Controller Replacement + Diode Mod
I ended up cutting the traces on the PCB and wiring in diodes for each switch. By doing that, I can take advantage of NKRO. This was a painful process but it turned out pretty good.

If you need any help, feel free to reach out.

Edit: My comment is specifically about the Epson QX-10 keyboard

Yeah I think this is the way to go and is my plan for my Epson (Q503A, btw). I will reach out to you when I get around to working on it. Thanks so much snacks!

[fireworm]

Fwiw, I cracked one of these (Q503A) open to find it already had diodes in it.

[OldIsNew]

Fwiw, I cracked one of these (Q503A) open to find it already had diodes in it.

The diodes definitely help. It's really just a matter of tracing out the matrix then and doing a Teensy type controller replacement. I've done this on a Fujitsu N860-2500-T111 board and a Data General 6242-A. On the Fujitsu board I initially tried leaving the controller components in place, but ultimately desoldered them because of problems with stay current.

Fujitsu board: viewtopic.php?f=7&t=17087&hilit=fujitsu


Data General: viewtopic.php?f=7&t=22869&hilit=fujitsu

I did do a Tandy board with no diodes. I added diodes to the shift keys and the keys on the shift columns so I wouldn't have problems using the shift keys, but didn't bother with diodes for the rest of the keys since I didn't really care about NKRO on that board.

Tandy 1000: viewtopic.php?f=2&t=17994&hilit=fujitsu